JP2007113036A - Cemented carbide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide cemented carbide having excellent toughness and corrosion resistance. <P>SOLUTION: There is provided (1) a cemented carbide in which a hard phase is composed of WC and a binder phase is composed of a Co-base alloy and in which the content of the Co-base alloy is made to 35 to 55 mass% and the Co-base alloy contains ≥20 mass% Ni and ≥6 mass% Cr, or (2) the cemented carbide composed of the above cemented carbide (1) in which Ni content and Cr content in the Co-base alloy are made to ≥30 mass% and ≥8 mass%, respectively. Further alternatively, there is provided (3) the cemented carbide composed of either of the above cemented carbides (1) and (2) in which the Co-base alloy contains 10 to 25 mass% W. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field related to cemented carbide, and particularly to the technical field related to cemented carbide excellent in toughness and corrosion resistance.

  Metals and ceramics generally have a tendency to decrease toughness when the hardness is increased. However, WC in which fine WC particles are dispersed in Co and / or Ni as a metal binder phase. In a -Co / Ni alloy, it is possible to suppress the inverse relationship between hardness and toughness by reducing the grain size of WC.

  Thus, cemented carbide has been devised as a material having high hardness and high toughness, eliminating the trade-off relationship between hardness and toughness. Therefore, in the cemented carbide, "WC-Co", "WC-Co + Ni", "WC-Ni", etc. are the basic components.

However, even with the above WC-Co cemented carbide, when the WC particles grow and become coarse in the sintering process when alloying the raw materials, the grain size becomes non-uniform. Both characteristics may be deteriorated. Therefore, in order to suppress the coarsening of WC particles, a method of adding a small amount of transition element carbide such as VC, TaC, TiC, Cr ₃ C ₂ is generally employed.

  Further, even if the above WC-Co based cemented carbide is annealed at about 800 ° C. (aging treatment), Co and / or Ni which are metal bonded phases (hereinafter also referred to as bonded phases) cause recrystallization. In some cases, pores (voids) are generated in the binder phase to reduce the hardness. Therefore, in order to suppress the generation of pores by strengthening the solid solution of the binder phase, a method of adding W has been used.

  Therefore, although cemented carbide has “WC-Co”, “WC-Co + Ni”, “WC-Ni”, etc. as basic components, the binder phase (bonding phase) is Co, Ni, V, Ta, Ti. , Cr and W are often alloys containing one or more of them.

  Cemented carbides are used for applications such as cutting tools, structural parts, machine parts, ornaments, and the like. Cemented carbides used for these applications require corrosion resistance as one of the required characteristics.

  For example, in cemented carbide used for cutting tools, the use of CFCs is restricted from the viewpoint of protecting the global environment when cutting with a lubricant, and water-soluble lubrication that can be washed with water after processing The agent is used in place of the oil-based lubricant. Thus, with the replacement of lubricants from oily to water-soluble, cemented carbides are required to have high corrosion resistance.

  Thus, when using a water-soluble lubricant as a lubricant, if the corrosion resistance of the cemented carbide of the cutting tool is insufficient, preferential corrosion of the binder phase occurs in the water-soluble lubricant, and WC particles fall off accompanying this. There arises a problem that the wear resistance is lowered due to, and the ablation wear resistance is lowered due to a decrease in hardness.

  Various evaluation methods can be considered for evaluating the corrosion resistance of the cemented carbide, but it is generally evaluated by immersing in a predetermined acidic or alkaline aqueous solution and the amount of corrosion weight loss. In addition, (1) a method of judging corrosion resistance based on the presence or absence of discoloration of the test piece after immersion, (2) a method of observing the test piece after immersion with an optical microscope, and examining the presence or absence of corrosion occurring on the surface (3) A method of measuring the elution amount after applying a water-soluble lubricant to a test piece and leaving it to stand for a predetermined time, (4) With the test piece immersed in a water-soluble lubricant, the surface is covered with a diamond file. An evaluation method such as a method of exposing the new surface by scratching and measuring the amount of accumulated current flowing between the test piece and the water-soluble lubricant at that time is also used.

As a cemented carbide in consideration of corrosion resistance, for example, there is one described in JP-A-10-298699. The cemented carbide described in JP-A-10-298699 includes 3 to 25% by mass of Co and Ni, and 0.1 to 3% by mass of chromium carbide with respect to Co and Ni, with the balance being It consists of WC and inevitable impurities. In this cemented carbide, WC corresponds to the hard phase, and Co and Ni (including chromium carbide) correspond to the binder phase, so the content of the binder phase (quantitative ratio of the binder phase to the cemented carbide) is 3 -25% by mass.
Japanese Patent Laid-Open No. 10-298699

  In conventional cemented carbides, the binder phase content is often 25% by mass or less (at most 30% or less). For example, in the case of the cemented carbide described in JP-A-10-298699, the binder phase content is 3 to 25% by mass.

  Since the cemented carbide with a low binder phase content has low toughness, problems such as cracking occur in applications that require toughness. For example, when cemented carbide is used after being bonded to a metal substrate, sufficient toughness is necessary to prevent cracking of the cemented carbide caused by the joining stress. A cemented carbide alloy with a small amount has a low toughness and is insufficient, so that there is a problem that cracks are likely to occur during joining.

  Thus, increasing the binder phase content can improve toughness, but a problem arises in that corrosion resistance decreases.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a cemented carbide excellent in toughness and corrosion resistance.

  As a result of intensive studies to achieve the above object, the present inventors have completed the present invention. According to the present invention, the above object can be achieved.

  The present invention thus completed and capable of achieving the above object relates to a cemented carbide, and is a cemented carbide according to claims 1 to 3 (a cemented carbide according to the first to third inventions). It has the following configuration.

  That is, the cemented carbide according to claim 1 is a cemented carbide in which the hard phase is made of WC and the binder phase is made of a Co-based alloy, and the content of the Co-based alloy is 35 to 55% by mass. It is a cemented carbide characterized in that the Co-based alloy contains Ni: 20% by mass or more and Cr: 6% by mass or more [first invention].

  The cemented carbide according to claim 2 is the cemented carbide according to claim 1, wherein the Ni content of the Co-based alloy is 30% by mass or more and the Cr content is 8% by mass or more. ].

  The cemented carbide according to claim 3 is the cemented carbide according to claim 1 or 2, wherein the Co-based alloy contains W: 10 to 25% by mass [third invention].

  The cemented carbide according to the present invention is excellent in toughness and corrosion resistance, and therefore can be suitably used as a cemented carbide alloy having high toughness and high corrosion resistance.

  The inventors of the present invention have made extensive studies in order to achieve the above-described object. As a result, the following knowledge was obtained.

(1) Among the components that make up cemented carbide, WC particles are ceramics and have excellent corrosion resistance. Therefore, WC (hard phase) does not affect the corrosion resistance of the cemented carbide.
(2) Of the components constituting the cemented carbide, the binder phase is a metal (alloy), and the corrosion resistance of the cemented carbide is governed by the component and composition of the binder phase.
(3) The corrosion resistance of cemented carbide is governed only by the chemical composition and composition of the binder phase. The structure and thermal history of the binder phase do not affect the corrosion resistance.
(4) In order to improve the corrosion resistance of cemented carbide, the binder phase is a Co-based alloy containing Ni and Cr (Co-based alloy), and the Ni concentration in the Co-based alloy is 20 mass% (wt%) As mentioned above, it is necessary to make Cr concentration 6 mass% or more. More preferably, the Ni concentration is 30% by mass or more and the Cr concentration is 8% by mass or more.
That is, from the viewpoint of improving corrosion resistance, an alloy based on Ni as a binder phase is not preferable, and an alloy based on a Co base and having Ni and Cr added simultaneously is preferable. A cemented carbide using a Co-based alloy having a Ni concentration of 20% by mass or more and a Cr concentration of 6% by mass or more as the binder phase provides excellent corrosion resistance. When the Ni concentration of the Co-based alloy is 30% by mass or more and the Cr concentration is 8% by mass or more, further excellent corrosion resistance can be obtained.
When the Ni concentration exceeds 50% by mass, it becomes a Ni-based alloy, and the corrosion resistance decreases. Therefore, the Ni concentration needs to be less than 50% by mass and not more than the Co concentration.
The corrosion resistance improves as the Cr concentration increases, but the toughness of the binder phase decreases as the Cr concentration increases. Therefore, the Cr concentration is desirably 20% by mass or less.
(5) When the binder phase (Co-based alloy) further contains 10% by mass of W, the corrosion resistance of the cemented carbide can be improved to a higher level. The higher the W concentration, the better the corrosion resistance. However, when the W concentration exceeds 25% by mass, the solid solution W precipitates as Co ₃ W, and the alloy strength (bonding phase strength) decreases. Therefore, it is desirable that W: 10 to 25% by mass is further contained in the Co-based alloy.
(6) In order to improve the toughness of the cemented carbide, the content of the binder phase (Co-based alloy) needs to be 35% by mass or more. However, if the content of this Co-based alloy exceeds 55% by mass, the hardness of the cemented carbide becomes too low and becomes insufficient, and the corrosion resistance decreases. Therefore, the content of the binder phase (Co-based alloy) needs to be 35 to 55% by mass.

  The present invention has been completed based on such findings. The cemented carbide according to the present invention thus completed is a cemented carbide in which the hard phase is made of WC and the binder phase is made of a Co-based alloy, and the content of the Co-based alloy is 35 to 55% by mass. In addition, it is a cemented carbide characterized in that the Co-based alloy contains Ni: 20% by mass or more and Cr: 6% by mass or more [first invention]. The cemented carbide according to the present invention is excellent in toughness and corrosion resistance, as can be seen from the aforementioned knowledge.

  Here, the content of the Co-based alloy (the content in the cemented carbide, that is, the quantitative ratio of the Co-based alloy to the cemented carbide) is 35 to 55% by mass, which is less than 35% by mass. In this case, the degree of improvement in the toughness of the cemented carbide is small and the toughness of the cemented carbide is low and insufficient, and in the case of exceeding 55% by mass, the hardness of the cemented carbide becomes too low and insufficient. At the same time, the corrosion resistance decreases.

  The Ni content in the Co-based alloy (the quantitative ratio of Ni to the Co-based alloy) is set to 20% by mass or more. When the Ni content is less than 20% by mass, the degree of improvement in the corrosion resistance of the cemented carbide is small. This is because the corrosion resistance of the hard alloy is low and insufficient. The Cr content in the Co-based alloy (the quantitative ratio of Cr to the Co-based alloy) is 6% by mass or more. When the Cr content is less than 6% by mass, the degree of improvement in the corrosion resistance of the cemented carbide is small. This is because the corrosion resistance of the hard alloy is low and insufficient.

  In the cemented carbide according to the present invention, it is desirable that the Ni content of the Co-based alloy is 30% by mass or more and the Cr content is 8% by mass or more [second invention]. This is because the corrosion resistance of the cemented carbide can be improved to a higher level.

Further, it is desirable that the Co-based alloy contains W: 10 to 25% by mass [third invention]. This is because the corrosion resistance of the cemented carbide can be improved to a higher level. In addition, although corrosion resistance improves, so that W density | concentration is high, the desirable value of an upper limit is 25 mass%. This is because when W is more than 25% by mass, solid solution W is precipitated as Co ₃ W, and the alloy strength (bonding phase strength) is lowered. From this point, the W content in the Co-based alloy is more preferably 13 to 20% by mass.

  Note that the higher the Cr content of the Co-based alloy, the better the corrosion resistance. However, as the Cr content increases, the toughness of the binder phase (Co-based alloy) decreases. From this point, the Cr content is preferably 20% by mass or less, and more preferably 12% by mass or less.

  As described above, the corrosion resistance of the cemented carbide is governed by the corrosion resistance of the binder phase (metal). That is, since WC does not corrode, the cemented carbide corrodes due to the corrosion of the binder phase. Therefore, one method for improving the corrosion resistance of the cemented carbide is to reduce the ratio (content) of the binder phase to the entire cemented carbide. In ordinary cemented carbide, the ratio of the binder phase is often 25% by mass or less (at most 30% by mass) in order to ensure corrosion resistance. However, such a technique for reducing the ratio of the binder phase makes it difficult to ensure toughness, and causes problems such as cracking in applications that require toughness. In particular, when cemented carbide is used by joining to a metal substrate, sufficient toughness is necessary to prevent cracking of the cemented carbide caused by the joining stress. A low cemented carbide has a low toughness and is insufficient, so that there is a problem that cracks are likely to occur during joining.

  On the other hand, in the cemented carbide according to the present invention, since the corrosion resistance of the binder phase itself is improved, the cemented carbide can have excellent corrosion resistance regardless of the ratio of the binder phase in the cemented carbide. Therefore, even a cemented carbide having a binder phase ratio of 35 to 55% by mass can have high corrosion resistance. Therefore, both high toughness and high corrosion resistance can be ensured.

  In the cemented carbide according to the present invention, the Co-based alloy of the binder phase contains Ni and Cr, or Ni, Cr and W as the alloy components, and is limited to containing only these elements. It is not a thing and elements other than these elements can be contained as needed, and unavoidable impurities can be included. When this Co-based alloy contains only Ni and Cr as alloy components, it can be said that this Co-based alloy is a Co-based alloy containing Ni and Cr, with the balance being Co and inevitable impurities. When this Co-based alloy contains only Ni, Cr and W as alloy components, it can be said that this Co-based alloy is a Co-based alloy containing Ni, Cr and W, with the balance being Co and inevitable impurities.

  Examples of the present invention and comparative examples will be described below. The present invention is not limited to this embodiment, and can be implemented with appropriate modifications within a range that can be adapted to the gist of the present invention, all of which are within the technical scope of the present invention. include.

[Example 1]
WC powder and Co-base alloy powder were blended so as to have a total weight of 1 kg, 5 kg of carbide balls and 700 cc of hexane were added thereto, and mixed for 4 hours with an attritor. After removing the cemented carbide balls from the mixture and drying the mixture, the mixture was formed into a green compact of 75 × 75 × 8 mm at a pressure of 1 ton / cm ² , and the green compact was placed in a nitrogen atmosphere in a vacuum furnace. Sintering was performed for 1 hour to obtain a sintered body, that is, a cemented carbide (No. 14 to 25). The hard phase of the cemented carbide is made of WC, and the binder phase is made of a Co-based alloy. The content of the binder phase (Co-based alloy) in the cemented carbide is 40% by mass (% by weight). The alloy composition of this binder phase (Co-based alloy) is as shown in Nos. 14 to 25 in Table 1.

  The cemented carbide (Nos. 14 to 25) was subjected to a corrosion test by the following method to evaluate the corrosion resistance.

That is, the above cemented carbide is processed into a coupon (test piece) having a size of 20 mm long × 20 mm wide × 3 mm thick, and this test piece is ultrasonically washed with pure water → acetone → IPA (isopropyl alcohol) and dried. after it was determined analytical balance weight and the weight measured in (electronic balance) each specimen (W _1). Moreover, the surface area (S) of each test piece was calculated | required. On the other hand, a pH 3 acetic acid aqueous solution was prepared as a test solution. At this time, the concentration of the test solution was previously determined by calculation to obtain a pH of 3, and after preparing the calculated concentration, the pH of the test solution was confirmed with a pH meter.

  Next, the test piece was immersed in the test solution for 6 hours (h). At this time, each test piece was placed in a Teflon (registered trademark) bottle together with 100 ml of the test solution, and this Teflon (registered trademark) bottle was immersed in a constant temperature water bath to maintain the temperature of the test solution at 60 ° C.

After the immersion, the test pieces were ultrasonically washed with pure water → acetone → IPA, dried, and then weighed with an analytical balance to obtain the weight (W ₂ ) of each test piece. Then, the difference _{(W 1 -W 2 = W 3} ) of the weight after immersion and the weight before immersion of each specimen determined, the weight difference between (W _3), the surface area of each specimen (S) and dip From time (6h), corrosion weight loss (g / m ² h) was determined and corrosion resistance was evaluated. Incidentally, a corrosion weight loss ^{(g / m 2 h) =} W 3 g / (Sm 2 · 6h) = W 3 / 6S (g / m 2 h), corrosion weight loss from the equation (g / m ² h) is Desired.

  Moreover, corrosion resistance evaluation was performed by performing a corrosion test on the commercially available cemented carbide alloys (No. a to No. e) in the same manner as described above. The hard phases of this cemented carbide are all made of WC, and some of the binder phases (No. b) are made of Ni-based alloys, while the others are made of Co-based alloys. is there. The content of the binder phase (Co-based alloy or Ni-based alloy) in the cemented carbide is 27% by mass in the case of No. a, 24% by mass in the case of No. b, and 30 in the case of No. c. In the case of No.d, it is 23% by mass, and in the case of No.e, it is 31% by mass. The alloy composition of the binder phase is as shown in No. a to No. e of Table 1.

  The alloy composition of the binder phase is determined by component / composition analysis of the binder phase. This analysis was performed as follows. That is, an analytical sample is taken from a cemented carbide, hydrochloric acid: 10 ml and water: 10 ml are added to this analytical sample, the binder phase is thermally decomposed, and after standing to cool, the solution is filtered, and the filtrate is used for each. Elements were quantified by ICP emission spectroscopy.

The results of the corrosion test (corrosion weight loss) are shown in Table 1. As can be seen from Table 1, the commercially available cemented carbides (No. a to No. e) do not satisfy the requirements of the cemented carbide according to the present invention, and the corrosion weight loss is 0.417 to 1.125 g / m ² h. It is.

Among the cemented carbides of Nos. 14 to 25, the cemented carbides of Nos. 14 to 16 and Nos. 18 to 23 do not satisfy the requirements of the cemented carbide according to the present invention, and the corrosion weight loss is 0.500 to 0.917. g / m ² h.

On the other hand, the cemented carbides of No. 17, No. 24, and No. 25 satisfy the requirements of the cemented carbide according to the present invention, and all of them have extremely small weight loss (0 g / m ² h). ), Excellent in corrosion resistance.

  In addition, as for the said cemented carbide alloy (No.14-25), as above-mentioned, all content of a binder phase (Co base alloy) is 40 mass% (weight%), The said commercially available cemented carbide alloy (No.a to No.e), more than (24 to 31% by mass), the cemented carbide (No.14 to 25) is the above-mentioned commercially available cemented carbide (No.a to No. It has better toughness than e). For example, the cemented carbide (No. 14 to 25) has a fracture toughness value of 1001 to 1157 MPa, which is higher than the fracture toughness value (880 to 956 MPa) of the commercially available cemented carbide (No. a to No. e). High and excellent toughness.

  Here, the fracture toughness value was determined as follows. That is, cemented carbide is processed into a 4mm x 3mm x 40mm test piece shape (SEPB method shape), and a cut is made at the center by wire cutting (width: 0.2mm, depth: 0.5mm). A three-point bending test was performed with the strength of the test piece fractured, and the strength (pressure) when the test piece broke was determined, and this was used as the fracture toughness value (the same applies hereinafter).

[Example 2]
Co-Cr-Ni ternary alloys (Co-based alloys) with various compositions were melted as the binder phase of the cemented carbide, and the corrosion resistance was evaluated by performing a corrosion resistance test on the binder phase alone. That is, the melted Co—Cr—Ni ternary alloy was processed into a coupon (test piece) having a size of 20 mm long × 20 mm wide × 3 mm thick, and this test piece was processed in the same manner as in Example 1 above. Corrosion resistance was evaluated by a corrosion test.

The results of the corrosion test (corrosion weight loss) are shown in Table 2. In Table 2, 3, 4, 6, and 8 in the right column of the Cr concentration (wt%) indicate Cr concentration values, and 20, 30, 35, and 40 in the column immediately below the Ni concentration (wt%). Indicates the Ni concentration value, and the other values indicate the corrosion weight loss (g / m ² h). Therefore, the corrosion weight loss (g / m ² h) in the case of each Cr concentration and Ni concentration. I understand. For example, when the Cr concentration is 6 wt% (wt%) and the Ni concentration is 40 wt%, it is found that the corrosion weight loss is 0.063 g / m ² h. As can be seen from Table 2, in the Co-Cr-Ni ternary alloy (Co-based alloy), when the Ni concentration is 20 wt% (wt%) or more and the Cr concentration is 6 wt% or more, the corrosion weight loss is 0.200 g / m. ² h or less, and exhibits excellent corrosion resistance. In particular, when the Ni concentration is 30 wt% or more and the Cr concentration is 8 wt% or more, the corrosion weight loss is 0.050 g / m ² h or less, and extremely excellent corrosion resistance is exhibited.

[Example 3]
After blending WC powder and Co-Cr-Ni-W quaternary alloy (Co-based alloy) powder to a total weight of 1 kg, they were mixed, dried and molded in the same manner as in Example 1. Thereafter, sintering was performed to prepare a cemented carbide having a hard phase made of WC and a binder phase made of a Co—Cr—Ni—W quaternary alloy (Co-based alloy). At this time, the alloy composition of the Co-based alloy of the binder phase was Cr content: 4.5 wt%, Ni content: 18.5 wt%, and the W content was variously changed. Note that the content of the binder phase (Co-based alloy) in the cemented carbide is 40% by mass.

The above cemented carbide is processed into a coupon (test piece) having a size of 20 mm long × 20 mm wide × 3 mm thick, and the test piece is subjected to a corrosion test in the same manner as in Example 1 to reduce the weight loss (g / m ² h) was determined.

The results of the corrosion test are shown in FIG. FIG. 1 summarizes the relationship between the W concentration (wt%) in the binder phase (Co-based alloy) of cemented carbide and the corrosion weight loss (g / m ² h) of the cemented carbide. As can be seen from FIG. 1, as the W concentration in the binder phase (Co-based alloy) increases, the corrosion resistance of the cemented carbide dramatically improves. When the W concentration is 10 wt%, the weight loss of the cemented carbide is reduced. Was reduced to about 0.4 g / m ² h. When the W concentration was 13 wt% or more, the corrosion weight loss of the cemented carbide became 0 g / m ² h. This is the result for the case where the Cr content in the binder phase (Co-base alloy) is 4.5 wt% and the Ni content is 18.5 wt%. The Cr content in the binder phase (Co-base alloy) is: Even in the case of 6 wt% or more and Ni content: 20 wt% or more, the corrosion resistance of the cemented carbide dramatically improved as the W concentration in the binder phase (Co-base alloy) increased, and the binder phase (Co-base alloy) When the Cr content is 6 wt% and the Ni content is 20 wt%, the corrosion weight loss of the cemented carbide is 0 g / m ² h when the W concentration is 10 wt% or more.

  Note that, as described above, the cemented carbide has a binder phase (Co-based alloy) content of 40% by mass (% by weight), and the above-mentioned commercially available cemented carbide (No. a to No. More than in the case of .e), the cemented carbide has higher toughness than the above-mentioned commercially available cemented carbides (No. a to No. e). For example, the cemented carbide has a fracture toughness value of 1037 MPa, which is higher than the fracture toughness values of the above-mentioned commercially available cemented carbides (No. a to No. e) and is excellent in toughness.

[Example 4]
The hard phase is made of WC, the binder phase is made of a Co-4.50Cr-18.7Ni alloy (Cr-based alloy: 4.50 wt%, Ni content: 18.7 wt% Co-based alloy), and the hard phase is made of WC Thus, a cemented carbide having a binder phase of Co-6.86Cr-28.7Ni (Cr-based alloy: 6.86 wt%, Ni content: 28.7 wt%) was produced by the same method as in Example 1. At this time, the content of the binder phase (Co-based alloy) (the ratio of the binder phase to the entire cemented carbide) was variously changed.

The above cemented carbide is processed into a coupon (test piece) having a size of 20 mm long × 20 mm wide × 3 mm thick, and the test piece is subjected to a corrosion test in the same manner as in Example 1 to reduce the weight loss (g / m ² h) was determined.

The results of the corrosion test are shown in FIG. FIG. 2 summarizes the relationship between the ratio (wt%) of the cemented phase metal (Co-based alloy) of the cemented carbide and the corrosion weight loss (g / m ² h) of the cemented carbide. As can be seen from FIG. 2, in the cemented carbide comprising the Co-4.50Cr-18.7Ni alloy (Co base alloy) as the binder phase ratio, the corrosion weight loss increased (corrosion resistance decreased). On the other hand, in the cemented carbide made of Co-6.86Cr-28.7Ni (Co-based alloy) as the binder phase, the corrosion weight loss was constant regardless of the binder phase ratio, and was almost 0 g / m ² h.

  In the cemented carbide alloy in which the binder phase is made of Co-6.86Cr-28.7Ni (Co-base alloy), the toughness is low when the content of the binder phase (Co-base alloy) is 25% by mass [the above-mentioned commercially available When the content of the binder phase (Co-based alloy) is 40 mass%, 50 mass%, and 60 mass%, the above-mentioned commercially available The toughness is superior to that of the cemented carbides (No.a to No.e). For example, when the content of the binder phase (Co-based alloy) is 40% by mass, the fracture toughness value is 1008 MPa, which is higher than the fracture toughness value of the above-mentioned commercially available cemented carbide (No.a to No.e). High and excellent toughness.

  Since the cemented carbide according to the present invention is a cemented carbide having high toughness and high corrosion resistance, it is required to have a high hardness, as well as a structural component, a mechanical component, a cutting tool (which is required to have excellent toughness and corrosion resistance). For example, it can be suitably used as a constituent material of a cutting tool in which a water-soluble lubricant is used as a lubricant, and it is extremely useful because its life is improved.

It is a figure which shows the corrosion test result of a cemented carbide, and is a figure which shows the relationship between W density | concentration in a binder phase, and corrosion weight loss. It is a figure which shows the corrosion test result of a cemented carbide, and is a figure which shows the relationship between a binder phase metal ratio and corrosion weight loss.

Claims (3)

  In a cemented carbide alloy in which the hard phase is made of WC and the binder phase is made of a Co-based alloy, the content of the Co-based alloy is 35 to 55% by mass, and the Co-based alloy is Ni: 20% by mass or more, Cr : A cemented carbide containing 6% by mass or more.   The cemented carbide according to claim 1, wherein the Co-based alloy has a Ni content of 30 mass% or more and a Cr content of 8 mass% or more.   The cemented carbide according to claim 1 or 2, wherein the Co-based alloy contains W: 10 to 25 mass%.

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